just a few questions about wiring

Tom, I "unpinned" the connectors when I did my harness. Meaning that I pulled the wire, pin and all from the plugs. I used a tiny screw driver with the end filed down with a dremel tool to depress the tang inside the plug to remove the wires with the pin attached.
I too had only the firewall up harness ( cut right off at the firewall ).
The main thing about the harness is deciding what to keep.

I kept the Power Distribution Center under the hood so that it continues to supply power and ground for all of the sensors and such. At that point it's as simple as grounding the ground block part of the PDC, connecting the battery to the main lug and jumping in the switched power from the stock ign switch and it'll light.

I even used one of the spare relay slots for the headlights.
You'll be surprised how much of the magnum harness can be removed once you get familiar with the diagrams.

I recommend keeping the wires for the ODBII connector and run it into the car ( even if you have to pull the in car connector from a junk yard) , that way you can check codes or add a pcm tuner in the future... I mistakenly removed the wires for mine...grrr